Enlarge (credit: jakeandlindsay) Microsoft's embrace and adoption of open source software has continued with the surprising decision to publish the code for Windows Calculator and release it on GitHub under the permissive MIT license. The repository shows Calculator's surprisingly long history. Although it is in some regards one of the most modern Windows applications—it's an early adopter of Fluent Design and has been used to showcase a number of design elements—core parts of the codebase date all the way back to 1995. The actual calculations are performed by this ancient code.